1. Field of the Invention
The present invention relates generally to a method of controlling beam scanning timing and beam energy and a light beam scanning apparatus using the method and, more particularly, to a method of automatically controlling refracted beam scanning timing and beam energy and a light beam scanning apparatus using the method.
2. Description of the Related Art
In general, optical signal processing has the advantages of high-speed processing, parallel processing and high-capacity processing capabilities, unlike conventional digital information processing that cannot process a large amount of data in real time. Research on the design and manufacture of a binary phase only filter, an optical logic gate, an optical amplifier, an image processing technique, an optical element and a light modulator is carried out using a spatial light modulation theory. The light modulator is applied to the fields of optical memory, an optical display, a printer, an optical interconnection and a hologram, and the research and development of a light beam scanning apparatus using the light modulator is being conducted.
Such a light beam scanning apparatus functions to produce an image by scanning a light beam and spotting the light beam on a light-sensitive medium in an image production apparatus, such as a laser printer, a Light Emitting Diode (LED) printer, an electrophotographic copier or a word processor.
Recently, with the development of a projection television, such a light beam scanning apparatus is being used as a means for scanning a beam onto an image display.
A light modulator is not necessarily applied to such a light beam scanning apparatus. For example, a conventional light beam scanning apparatus shown in FIG. 1 is not provided with a light modulator. The construction of the conventional light beam scanning apparatus is described in detail below.
Referring to FIG. 1, the conventional light beam scanning apparatus includes a light source 110, a control unit 120, a lens 130, a rotating mirror 140, an F-theta lens 150, a focusing lens 160, and a horizontal synchronization signal sensor 170.
The light source 110 may be implemented with a laser or laser diode that generates a laser beam. The light source 110 generates a laser beam while being turned on/off according to the operation control of the control unit 120.
The control unit 120 receives a timing value for beam scanning from the horizontal synchronization signal sensor 170, and controls the on/off operation of the light source 110 and the operation of the rotating mirror 140.
The lens 130 focuses a laser beam, generated by the light beam 110, toward the reflecting surface of the rotating mirror.
The rotating mirror 140 is turned on/off according to the operation control of the control unit 120, and is rotated at a preset uniform rotational velocity during operation. The rotating mirror 140 is implemented with a polygonal rotating mirror, so that it reflects an incident beam using the reflecting surface thereof while rotating. In this case, a beam reflected by a reflecting surface of the rotating mirror 140 is scanned onto a scanning object 180 while forming a beam spot arrangement with spots arranged at regular intervals. The beam spot arrangement is formed in a line along the length of the scanning object 180. Although a beam reflected by the next reflecting surface also forms a beam spot arrangement along the length of the scanning object 180, this beam spot arrangement is located below the previous beam spot arrangement while being spaced apart from the previous beam spot arrangement by a specific interval. As a result, the beam spot arrangements formed by the beams reflected by the reflecting surfaces of the rotating mirror 140 are formed along the length and circumference of the scanning object 180.
The rotating mirror 140 is equipped with a motor (not shown). The rotating mirror 140 reflects a beam, emitted through the lens 130, toward the scanning object 180 while being rotated by the motor. Such a rotating mirror may be implemented with a polygon mirror or Galvano mirror.
When the polygon mirror is employed as the rotating mirror 140, the rotating mirror 140 becomes characterized by moving a beam emitted through the lens 130 at uniform velocity.
When the Galvano mirror is employed as the rotating mirror 140 the rotating mirror 140 becomes characterized by moving a beam, emitted through the lens 130, at nonuniform velocity.
The F-theta lens 150 scans a beam, scanned by the rotating mirror 140, onto the scanning object 180 while keeping scanning velocity uniform by keeping the scanning distance between the current reflecting surface of the rotating mirror 140 and the scanning surface of the scanning object constant, thus adjusting the interval between the spots of a beam spot arrangement to a constant distance. Depending on whether the F-theta lens 150 is present, the interval between the spots of a beam spot arrangement, formed on the scanning object 180, varies. The examples are illustrated in FIGS. 2a and 2b. 
FIG. 2a shows a beam spot arrangement formed on the scanning object 180 in the case where the conventional light beam scanning apparatus is equipped with the F-theta lens 150. In this case, the beam spots are regularly arranged.
FIG. 2b shows a beam spot arrangement formed on the scanning object 180 in the case where the conventional light beam scanning apparatus is not equipped with the F-theta lens 150. In this case, the beam spots are irregularly arranged.
The focusing lens 160 focuses a beam scanned through the F-theta lens 150, and scans the beam on the scanning object 180.
The horizontal synchronization signal sensor 170 receives a reference beam spot indicating the start of printing or image display from the rotating mirror 140, sets timing for beam scanning time, which starts from the time when the reference beam spot is received, with respect to a current reflecting surface, and outputs a timing value to the control unit 120. At this time, the horizontal synchronization signal sensor 170 sets the timing for beam scanning time that extends to the time of receiving a reference beam spot reflected by the reflecting surface next to the current reflecting surface.
Though the conventional light beam scanning apparatus employs an F-theta lens to keep the interval between the beam spots of a beam spot arrangement constant on a scanning object, the F-theta lens is disadvantageous in that a long developing period is required and high manufacturing cost is incurred due to difficulty with manufacture and design.
Furthermore, a conventional light beam apparatus equipped with a light modulator keeps the interval between the beam spots of a beam spot arrangement constant using the F-theta lens. In this case, the same disadvantages are incurred because the F-theta is employed.